In recent years, according to its light, thin, low power consumption properties, an Flat Panel Display (FPD), such as liquid crystal display panel, has been widely used in a variety of fields, for examples a television, a car navigation and a compute. A panel size is being increased every year and a demand for a zero-defect of pixels is required, so that a repair method of a defect part is required to improve the productivity in the manufacturing. The liquid crystal display panel has a pair of substrates facing each other, a gap between the substrates is kept constant by a spacer and a liquid crystal fill up between the substrates. One substrate is an active matrix array substrate, on which thin film transistors (hereinafter, referred to as TFTs) and pixel electrodes to be connected to the TFTs is formed. The other substrate facing the array substrate is usually provided with a color filter (hereinafter, referred to as CF). The substrate having the CF formed thereon is also referred to as color filter substrate (CF substrate).
A conductive film is respectively formed on each substrate. A driving of the liquid crystal is controlled by electrical charges that are accumulated between the conductive films. It is difficult to control the liquid crystal near a transistor formation part or wiring part of the TFT, compared to the liquid crystal in a display part configuring the pixels. Accordingly, a light shield area (hereinafter, referred to as BM) is formed on the CF side to suppress light transmission, so that a beautiful display is made.
The array substrate has a plurality of independent pixels. However, in any one during the TFT manufacturing process, if an abnormal pattern is caused or a foreign material or impurity is introduced between the array substrate and the opposite substrate (CF substrate), the pixel is to be a luminescent point defect that the pixel is brighter than the surrounding, so that a quality is degraded. Even though one of millions of pixels has the luminescent point defect, it may be considered as a defective product, because a market demand for a high-quality liquid crystal panel having no luminescent point is increased. As countermeasure of the generation of the defect, a repair method becomes more important. That is, it is possible to improve the yield or quality by a relatively simple method of repairing one defect of millions of pixels.
As the method of repairing a pixel having a luminescent point defect that is brighter than the surrounding pixels, a method is known in which the luminescent point defect is turned into a dark point so that the pixel is not more remarkable than the surrounding pixels. The method of turning a luminescent point defect into a dark point (turning-into-dark point) is performed to display the pixel in black all the time. As a repair method of the turning-into-dark point, there is a method of connecting a pixel electrode to a gate by irradiation of laser light and then applying a constant voltage to display the black. This is effective when the pattern defect is caused in the TFT. However, the method has a demerit that it cannot be used for a defect that is caused due to the foreign material introduced to the liquid crystal between the array substrate and the CF substrate, for example. Also, the strength of the connection part, to which the laser light is irradiated, is lower than a normal part. Accordingly, the connection part may be disconnected later, so that the luminescent point defect may be caused again.
Other than the method of electrically controlling the turning-into-dark point, the turning-into-dark point is darkened by coloring of the pixel itself. For example, there is a technology of mixing microcapsules having carbons included therein in a color material of the CF and irradiating the laser to diffuse the carbons in the color material (refer to JP-A-H04-361228) and a technology of scraping a black part of a BM of the CF by irradiating the laser to the BM to diffuse the same into the color material and glass and thus achieving the turning-into-dark point (refer to JP-A-2011-504599).